A FULL-Multi-Operator Core Network (FULL-MOCN) features a common radio access network (RAN) that is shared by multiple Mobile Switching Centres (MSCs) and/or Serving GPRS Support Nodes (SGSNs), where each MSC and/or SGSN is associated with a different Public Land Mobile Network (PLMN). Thus, a FULL-MOCN allows multiple core network operators to share a single RAN. This is a departure from the traditional implementation where a single RAN is associated with a single operator.
When a Mobile Station (MS) leaves a source cell and enters a target cell that supports MOCN, the MS needs to execute a handover procedure. Following the handover procedure, the MS may need to communicate a routing area update (RAU) message in the target cell if a change in routing area identity (RAI) occurs. A change in RAI can occur if the PLMN that served the MS in the source cell is different from the PLMN that will serve the MS in the target cell. A change in RAI can also occur if the location area code (LAC) or routing area code (RAC) of the source cell is different from the LAC/RAC of the target cell. Although it is desirable for the MS to maintain PLMN continuity across a handover, it is not always possible. If the PLMN that serves the MS changes across handover, then a change in RAI occurs, and the MS should communicate a RAU upon completion of the handover. However, if the RAI does not change across the handover (i.e., PLMN continuity is maintained across the handover and the LAC/RAC of the target cell is the same as the LAC/RAC of the source cell), then a RAU is unnecessary.
With the increase in popularity of mobile devices, it is important that handover of a MS from a source cell to a target cell is performed seamlessly and efficiently in a FULL-MOCN environment. The introduction of FULL-MOCN presents a shift in network implementation that can affect various operations of the network including handover and RAU procedures.